The present invention relates to a wicket gate mounting with adjustable play, particularly for water turbines.
A turbine includes wicket gates which are arranged around a turbine axis. Wicket gates are also sometimes referred to as guide vanes. The orientation of each wicket gate around a respective axis parallel to and radially outward of the turbine axis is to be adjusted, and a respective wicket gate stem supports the wicket gate at the respective axis.
Wicket gate stems are mounted using maintenance-free slide bearings which do not require any grease or oil lubrication. The slide bearing uses a layer of slide material, consisting substantially of polytetrafluorethylene. The layer can be produced only with relatively large tolerances, leading to unfavorable conditions of bearing play. Furthermore, under certain operating conditions, particularly for pump turbines, brief rotational and flexural vibrations of the wicket gates occur. When these are increased by excessive bearing play in addition to the normal wear, it results in increasing wear of the layer of slide material. This is discussed in Publication No. t 2428 distributed by J. M. Voith, GmbH, assignee hereof.
Federal Republic of Germany DE-OS No. 35 01 731 describes a radial slide bearing of the aforementioned type in which an outer bushing has a circular cylindrical inner bore. Within that bore, an inner multipartite bushing is seated in both radially and axially immovable fashion. A layer of slide bearing material is attached to the inner bushing only in individual sections distributed over the circumference of the bearing. The layer of material in the remaining circumferential region can be lifted off from the inner bushing by the action of a hydraulic pressure fluid introduced between the layer and the bushing. In this way, this bearing can be adjusted free of radial play.
This, however, requires a suitably developed, fail-proof supply of pressure fluid. Furthermore, the escape of fluid from the space between the inner bushing and the layer of slide bearing material must be avoided. The presupposes an effective sealing of the individual parts of the inner bushing with respect to each other and with respect to the layer of slide bearing material. Viewed as a whole, this known bearing embodiment is very expensive, and it is not completely dependable in operation.